Jean-Claude Bunzli - A p-tert-butylcalix[4]arene functionalised at its lower rim with ether-amide pendant arms acts as an inorganic-organic receptor: structural and photophysical properties of its lanthanide complexes

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      Publication Details (including relevant citation   information):

      Ramirez,F.D., Charbonniere,L., Muller,G., Scopelliti,R.,   Bunzli,J.C.G. Journal of the Chemical Society-Dalton   Transactions 2001 (21) 3205-3213

      Abstract: The new narrow-rim functionalised   receptor   5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis[2-(diethylcarbamoylmethoxy)   ethoxy] calix[4]arene (A(4)bL(4)) has been synthesised. NMR   spectra show it to adopt a cone conformation in solution with a   time-averaged C-4v symmetry. A(4)bL(4) reacts with trivalent   lanthanide ions in acetonitrile to yield 1:1 complexes with   logK(1) in the range 8.6-9.6, as demonstrated by ES-MS, H-1- and   C-13-NMR data. Complexes with Ln = Eu, Gd, Tb, and Lu have been   isolated and the crystal structure of   [Lu(A(4)bL(4))(H2O)](CF3SO3)(3). 2Et(2)O shows the metal ion   encapsulated in the cavity formed by the four arms. Lu-III is   9-co-ordinated, being bound to the four ether and four carbonyl   functions and to a water molecule itself H-bonded to the phenolic   ether functions, which rigidifies the cavity formed by the   pendant arms. Additionally, an ether molecule is inserted into   the hydrophobic cavity defined by the aromatic rings. Both NMR   (La, Lu) and luminescence (Eu, Tb) data point to a fairly high   local symmetry at the metal centre, while lifetime determinations   are consistent with the co-ordination of an inner-sphere water   molecule. The new ligand sensitises the luminescence of the   Tb-III ion (Q(abs) = 5.8% in acetonitrile, tau (F) = 1.42 ms)   while the probable presence of a LMCT state severely limits such   a process for Eu-III : Q(abs) = 2.0%, tau (F) = 0.73 ms

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